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Author Topic: Help with Motor Overheating!  (Read 29498 times)

Online Crist Rigotti

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Re: Help with Motor Overheating!
« Reply #50 on: August 14, 2015, 12:43:27 PM »
I'm back home and on to curing the motor overheating problem.  I bought a Cobra 3515/18 740Kv motor and will be installing this along with a few other small changes.  Stay tuned!
Crist
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Online Crist Rigotti

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Re: Help with Motor Overheating!
« Reply #51 on: August 14, 2015, 04:18:37 PM »
OK, here's what I did to go from a Cobra 2826/12 760Kv to a 3515/18 740Kv motor.  The 3515 motor od about 3/8 diameter larger than the 2826 motor.  I used my carbide ball grinder that I extended using a piece of 5/32 od brass tubing and a couple inches of 1/8 music wire all soldered together and chucked up in my Dremel tool.  I ground out the top blocks and the side tri pieces.  I sealed them using some SIG-Ment.  I then fashioned some 1/8 spacers out of 1/8 thick PC circuit board having a diameter of 3/8 with 1/8 hole for the motor mounting screws.  These were epoxied in place using some 4-40 screws and nuts.  The screws were greased near the top so they wouldn't get glued in!

After that I redid my disconnect plug and shortened the motor wires about 3/4 inch.  I then covered them with heat shrink and installed everything.  All ready to go out and see what happens!  Perhaps Saturday morning!

Crist
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Offline Target

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Re: Help with Motor Overheating!
« Reply #52 on: August 14, 2015, 06:48:12 PM »
Good luck with the re-maiden. Super curious how this will work compared to the other setup.
Regards,
Chris
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Online Crist Rigotti

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Re: Help with Motor Overheating!
« Reply #53 on: August 15, 2015, 09:56:49 AM »
Ok, I flew it this morning.  The results were very encouraging!  Air temp was 76 degrees.

Without spinner  Motor temp = 112    Battery temp = 112
With spinner    Motor temp = 128.4    Battery temp = 109

The set up wasn't changed except for the motor.  The same prop, ESC settings, same timer settings, etc.

It also looks like just about the same MAH draw on the batteries with the larger motor.  I'll know more when I charge them up the next time out.

I think I'll add a small baffle to direct the air more towards the motor.  The L-40 has a long slope to the nose area and the majority of the inlet opening is behind the motor.

Then I'll explore a vented spinner.....maybe.

Thanks to everyone and their input.  Will, you were right on.
« Last Edit: August 15, 2015, 10:40:44 AM by Crist Rigotti »
Crist
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Online Fred Underwood

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Re: Help with Motor Overheating!
« Reply #54 on: August 15, 2015, 10:53:52 AM »
So, is it the motor, or the fan, or the combination? At least I believe that you have the fan on the 35 series as shown.  Did you try it with the fan off for curiosity?
Fred
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Offline William DeMauro

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Re: Help with Motor Overheating!
« Reply #55 on: August 15, 2015, 11:46:58 AM »
Crist,
   I'm becoming more and more convinced that the 35 series Cobra's work way better for most of our needs and that they should be used in place of any equivalent 28 series motors whenever possible if they will fit. Joe Daly jr has a similar problem with Rounder last week and is also switching to the 3515. I have not run my motor with the fan off it so I don't know what the effect will be. All I know is that its working so well I don't want to change anything. I do have an baffle on my inlet I'm sure that helps. BUT keep in mind I also ELIMINATED the vented spinner so I did take a cooling source away too. I flew today in 90+ temp and while I never took an actual temperature  my motor was not even warm to the touch. It was coming down as though it was never run. I cant ask for better than that. To me this means all my battery energy is going to the prop and not into making heat. This makes for a very efficient system.
William
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Online Crist Rigotti

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Re: Help with Motor Overheating!
« Reply #56 on: August 15, 2015, 07:02:57 PM »
So, is it the motor, or the fan, or the combination? At least I believe that you have the fan on the 35 series as shown.  Did you try it with the fan off for curiosity?

Fred,
I really don't know.  Though I suspect the motor was the big fix.  In reality, I think the fan doesn't do that much cooling.  I'm with Will in that the fan is on so I'll leave it on.  Maybe when I get more adventurous, I'll do some testing with it off.
Crist
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Re: Help with Motor Overheating!
« Reply #57 on: August 15, 2015, 09:28:39 PM »
Really glad it worked out for you, Christ.
Regards,
Chris
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Online Fred Underwood

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Re: Help with Motor Overheating!
« Reply #58 on: August 16, 2015, 02:26:59 PM »
Crist,
Great that the overheating is solved.  Just my curiosity, and a little help for others, about with and without the fan.  Good for you to be able to concentrate on flying again.
Fred
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Online Crist Rigotti

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Re: Help with Motor Overheating!
« Reply #59 on: August 16, 2015, 03:10:16 PM »
Thanks Fred.  I'll let everyone know when I do more testing and the results.
Crist
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Online Dennis Toth

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Re: Help with Motor Overheating!
« Reply #60 on: August 17, 2015, 11:56:49 AM »
Crist,
One thing that has worked well for me is to make sure the air outlets is at least 125% of the inlet. As the air flows over the motor/battery and picks up heat it expands and you need more outlet area to care that heated air out. I have a Stuka with the same cowl as used on the IC version with a baffle to kick the air up toward the motor and an additional outlet at the back of the tank portion of the cowl. For my ships I like a clean spinner and spinner fit to the fuse. Big outlets keep the air flowing nicely.

Best,   DennisT

Online Crist Rigotti

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Re: Help with Motor Overheating!
« Reply #61 on: August 17, 2015, 12:17:12 PM »
Crist,
One thing that has worked well for me is to make sure the air outlets is at least 125% of the inlet. As the air flows over the motor/battery and picks up heat it expands and you need more outlet area to care that heated air out. I have a Stuka with the same cowl as used on the IC version with a baffle to kick the air up toward the motor and an additional outlet at the back of the tank portion of the cowl. For my ships I like a clean spinner and spinner fit to the fuse. Big outlets keep the air flowing nicely.

Best,   DennisT

Thanks Dennis on that info.  My outlet is about 2.5 times the air inlet.  I think the slope of the nose cowl is my biggest problem right now.  It angles back so far putting in an effective baffle to direct the air more upward toward the motor will be a bit of a challenge.

Crist
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Online Fred Underwood

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Re: Help with Motor Overheating!
« Reply #62 on: August 17, 2015, 02:48:30 PM »
Stating the obvious, a front mounted motor has most of the air inlet behind the motor mount and motor, and most are fairly sloped back.  Perhaps the baffle acts as a bit of a dam to help air up toward the front and perhaps the fan is then more effective with a cool air supply.  I did the fan, and then the baffle, each helped an increment.  I cut a thin saw line to each side of the opening, guessed the angle and inserted a piece of 1/32 ply and a little Ca.  It could have been removed, and repositioned, but worked well enough to stay. Perhaps there is a more scientific approach to position and angle but it did not seem so earlier in the thread.

Good news is that you already have an adequate solution, though it may still be a bit hot in 90 degrees and up.
Fred
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Offline Motorman

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Re: Help with Motor Overheating!
« Reply #63 on: August 19, 2015, 05:14:27 PM »
The hole is too far back, you're getting natural draught cooling. Maybe make a baffle but, it's not going to be ram air just a high pressure area that's hopefully higher pressure than the vent in back of the motor.  

You made changes for electric system in the fuel tank area but, you're compromised with the cooling hole of a glow engine. We need a design that's dedicated to electric.

Why don't you re-construct the bottom of the cowl to have a big ram air scoop right under the spinner that would funnel the air up in front of the fire wall and through the motor. It doesn't have to be as big as a navy A7.

MM

P.S. That spinner thing looks like a whiffle ball.
« Last Edit: August 19, 2015, 05:32:34 PM by Motorman »

Online Crist Rigotti

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Re: Help with Motor Overheating!
« Reply #64 on: August 19, 2015, 09:01:24 PM »
The hole is too far back, you're getting natural draught cooling. Maybe make a baffle but, it's not going to be ram air just a high pressure area that's hopefully higher pressure than the vent in back of the motor.  

You made changes for electric system in the fuel tank area but, you're compromised with the cooling hole of a glow engine. We need a design that's dedicated to electric.

Why don't you re-construct the bottom of the cowl to have a big ram air scoop right under the spinner that would funnel the air up in front of the fire wall and through the motor. It doesn't have to be as big as a navy A7.

MM

P.S. That spinner thing looks like a whiffle ball.


I tried to build a faithful rendition of Alan's Legacy 40 which included the slope of the nose.  If I did it all over, then yes, I would redesign the slope/nose area.
« Last Edit: August 20, 2015, 08:48:18 AM by Crist Rigotti »
Crist
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Offline John Cralley

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Re: Help with Motor Overheating!
« Reply #65 on: August 19, 2015, 09:16:34 PM »
Crist, You did Alan's Legacy 40 proud and l'm sure he would be pleased!

I think you have a handle on the cooling and l'm eager to hear how the model trims out!
John Cralley
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Online Crist Rigotti

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Re: Help with Motor Overheating!
« Reply #66 on: August 24, 2015, 12:35:31 AM »
Thanks John.

I fabricated and installed a baffle tonight.  I made it from 1/32 ply and epoxied it in.  I'll show the front view later today when the glue cures.

Here is what the baffle looks like.

Crist
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Online Crist Rigotti

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Re: Help with Motor Overheating!
« Reply #67 on: August 24, 2015, 08:32:00 AM »
Here is what the baffle looks like when installed.  I kept the end closest to the motor ahead of the fan.  I didn't what all the ram air to blow on the fan, thus reducing its effectiveness drawing air through the motor.

Now I'll do some test flights this week and report back.

Crist
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Offline Curare

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Re: Help with Motor Overheating!
« Reply #68 on: August 24, 2015, 09:50:42 PM »
I'll be watching to see what change, if any the baffle has to your temps.

Greg Kowalski
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Online Crist Rigotti

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Re: Help with Motor Overheating!
« Reply #69 on: August 26, 2015, 12:28:09 PM »
I took it out this morning.  Flew 3 flights.  Outside air temp was about 80 to 85 degrees.

Flight 1 - Motor 109 degrees  Battery 106 degrees.  The motor was warm to the touch, no problem holding your finger on the motor.
Flight 2 - Motor 115 degrees  Battery 112 degrees.  The motor was warmer to the touch, no problem holding your finger on the motor.
Flight 3 - Motor 112 degrees  Battery 112 degrees.

Success!  On flights 2 and 3 I even worked on trimming the plane!

I'm a happy camper.

Thanks to all for their help.
« Last Edit: August 26, 2015, 04:18:31 PM by Crist Rigotti »
Crist
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Re: Help with Motor Overheating!
« Reply #70 on: August 26, 2015, 07:09:55 PM »
Sweet, Christ. Glad to hear it worked out for you.
Sounds like the 35 series makes a big difference, and that fat motors might be better to use where they will fit.
I'll be keeping that in mind for future projects.

R,
Chris
Regards,
Chris
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Online Crist Rigotti

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Re: Help with Motor Overheating!
« Reply #71 on: August 29, 2015, 08:13:13 PM »
Flew 4 flights today.  Motor temps were about 105 degrees.  80 degree outside air temps.
Crist
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Offline Jason Greer

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Re: Help with Motor Overheating!
« Reply #72 on: August 29, 2015, 08:19:17 PM »
Wonderful, glad you got it sorted out. And just in time to get it good and trimmed for the El Dorado meet up here in Arkansas in November! :)
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Online Crist Rigotti

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Re: Help with Motor Overheating!
« Reply #73 on: August 29, 2015, 09:56:07 PM »
Wonderful, glad you got it sorted out. And just in time to get it good and trimmed for the El Dorado meet up here in Arkansas in November! :)

Yup, working on trimming the airplane now.
Crist
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